Pompeo was supposed to visit earlier this month but was forced to postpone his visit because of unrest at the U.S. Embassy in Iraq after deadly U.S. airstrikes.

Some observers predict that due to recent events, this could be a tricky trip.

Last week, Pompeo became embroiled in a spat with an NPR journalist, reportedly asking her after an interview, "Do you think Americans care about Ukraine?" The State Department removed a different NPR reporter, Michele Kelemen, from this week's trip to Europe.

When asked about the interview while en route to London on Wednesday, and the allegation he said Americans don't care about Ukraine, Pompeo told reporters: "I just rolled through a lot of really important things going on in the world."

He added that there was "a lot of history with NPR and Mike Pompeo and Iran" going back to 2015. He would however talk to NPR again, he said.

The trip comes just weeks after Iran shot down a Ukrainian airliner, which was followed by an indicted associate of Rudy Giuliani, a personal attorney for Trump, saying in an interview that the president "knew exactly what was going on" regarding the central claim of the impeachment process: that the administration attempted to pressure the Ukrainian government to dig up dirt on former Vice President and current Democratic presidential candidate Joe Biden.

"This has been a very intense month," said Mykola Kapitonenko, an associate expert at the International Center for Policy Studies, a think tank in Ukraine. "This has created a totally different background for the upcoming visit compared to what it had been a month ago."

Pompeo is visiting Ukraine as part of a tour that also encompasses the United Kingdom, Belarus, Kazakhstan and Uzbekistan.

He will talk with President Volodymyr Zelenskiy to "highlight U.S. support for Ukraine’s sovereignty and territorial integrity," meet with business leaders, and lay a wreath to commemorate Ukrainian soldiers who have died fighting Russian-backed separatists in the east of the country, according to the State Department.

Pompeo was forced to postpone the initial trip Jan. 1 because of protests around the U.S. Embassy in Baghdad, triggered by U.S. airstrikes on weapons depots in Iraq and Syria that killed at least 25 militia fighters. Following a subsequent U.S. drone attack that killed one of Iran’s top military commanders, Qassem Soleimani, Tehran responded with missiles directed at Iraqi bases hosting American troops, around the same time shooting down a Ukraine International Airlines passenger plane, killing all 176 people aboard.

Pompeo's Ukraine trip was always going to be closely scrutinized given the country's connection to Trump's impeachment trial. The president is accused of freezing aid and withholding an Oval Office visit for Zelenskiy unless Ukraine helped investigate Biden, a political rival of Trump.

Despite these events, the core purpose of the secretary's visit will remain to address the relationship between Washington and Kyiv that has slipped from a strategic partnership into one of "political gambling and distrust," Kapitonenko said. "Trump feels uncomfortable about Ukraine, while Volodymyr Zelenskiy is suspicious about the U.S."

There are plenty of mutual interests and reasons why the U.S. and the wider West should care about Ukraine, according to Kapitonenko, who described their relations as being "very stable on the one hand, but rather vulnerable on the other."

Ukraine is on the front line between Russia and the West, the site of by Europe's only active military conflict. Some 14,000 people have been killed since rebels backed by Russian President Vladimir Putin began fighting for independence in the country's east.

The U.S. has provided support in the form of equipment and training for Ukrainian troops.

"Ukraine is defending itself and the West against Russian attack," William Taylor, a former U.S. ambassador to Ukraine who testified during Trump's impeachment hearings, wrote in a New York Times opinion piece Sunday. "If Ukraine succeeds, we succeed. The relationship between the United States and Ukraine is key to our national security, and Americans should care about Ukraine."

For their part, the Ukrainians will hope that Pompeo arrives as a representative of the U.S. government, rather than an outrider for Trump's presidential campaign, according to Alyona Getmanchuk, director of the New Europe Center, a think tank based in Kyiv.

"Hopefully Mike Pompeo during his visit will make it clear that despite the internal situation in the U.S., Washington remains Ukraine's ally in the war with Russia," she said.

Getmanchuk added that she hopes the secretary of state is not on a "special mission" to tell Ukraine how it "should act, and not act, with regard to the impeachment issue."

Alexander Smith reported from London and Oksana Parafeniuk reported from Kyiv.